JP7349655B2 - projection device - Google Patents

Description

The present invention relates to a projection device for distance measurement.

Conventionally, distance measurement methods include phase difference detection methods, which perform amplitude modulation on the light from a light source and measure the phase difference between the light reflected from the object under test and the light source, and irradiate extremely short pulses of light to measure the phase difference between the light source and the object to be measured. The TOF (Time of Flight) method is known, which measures distance by measuring the arrival time of reflected light.

Here, in order to increase the measurable distance and increase the measurement accuracy, it is necessary to use a semiconductor laser as a light source in order to obtain high frequency modulation or a very short pulse waveform with a small size and high output.

The use of laser light sources is regulated in Japan by JIS-C6802 from the viewpoint of safety for the human body and eyes. In particular, if there is a possibility that light may enter people's eyes, it is generally necessary to satisfy the conditions of class 1.

Here, in order to satisfy the conditions of class 1 and increase the output of the laser light source, it is necessary to increase the beam diameter of the laser light in the diffuser plate disposed on the exit surface of the projection device.

Specifically, if the beam diameter at the exit surface of the projection device is small, when a person looks at the projection device, the light source image formed on the retina of the eye will also become smaller, increasing the concentration of light and causing damage to the eyes. Cheap. In order to prevent this, the light source image formed on the retina can be made larger by increasing the beam diameter of the exit surface of the projection device. Thereby, the maximum value of the light output of the laser light source can be increased without causing damage to the eyes.

By the way, as a conventional laser projection device, there is one having a configuration in which a diffuser plate is disposed in a window of an emission part of a semiconductor laser (see, for example, Patent Document 1).

In the invention of Patent Document 1, light emitted from a laser light source is diffused and expanded by a concave lens, and the light is projected onto a diffuser plate. In the diffuser plate, light is diffused in the same direction. By using a concave lens, the beam diameter at the diffuser plate is increased.

Here, the beam diameter of the laser light source is very small, several μm, but by using a concave lens and a diffuser plate, it is possible to form a beam diameter on the diffuser plate that is much larger than the beam diameter at the exit surface of the laser light source. become.

As a result, when a person looks into the laser, the image of the light source formed on the retina of the eye becomes larger, so the upper limit of the laser output can be increased without causing damage to the eyes.

Japanese Patent Application Publication No. 9-307174

By the way, in conventional inventions, the emitted light from the laser light source is spread by a concave lens and irradiated onto the diffuser plate, so in order to increase the apparent beam diameter of the laser light source, it is necessary to make the diffusivity of the diffuser plate extremely high. There is.

Specifically, in the central portion of the diffuser plate, light enters the incident surface of the diffuser plate substantially perpendicularly, but in the peripheral portion, light enters the incident surface of the diffuser plate obliquely. Therefore, in order to emit similar diffused light at the center and periphery of the diffuser plate, the diffusivity must be strong enough to be independent of the angle of incident light.

Furthermore, if the apparent beam diameter of the laser light source on the diffuser plate is small, the brightness of the light source will be high, which may cause damage to the eyes of people looking at the projection device. Therefore, in order to ensure the laser safety of the projection device, it is necessary to use a diffuser plate with extremely high diffusivity to increase the apparent beam diameter at the surface of the diffuser plate.

However, with a typical ground glass diffuser, light is diffused by multiple reflections on the ground glass portion, so increasing the light diffusivity increases the proportion of light that returns from the diffuser surface to the laser light source. Utilization efficiency will drop significantly.

Furthermore, the diffusion characteristics of a highly diffusive diffusion plate are generally Lambertian diffusion, which weakens light in oblique directions. Furthermore, since the diffusion surface is a flat plate, there is a problem in that light cannot be diffused over 180 degrees.

The present invention has been made in view of these points, and an object thereof is to provide a projection device that can emit uniform light with a wide radiation angle and a small light loss at the diffuser plate.

A first invention is directed to a projection device, and includes a triangular prism having a first surface, a second surface, and a third surface, a light source that emits light to the first surface of the prism, and a light source that emits light to the first surface of the prism. two diffusers disposed opposite to the second surface and the third surface, respectively, and the apex angle formed by the second surface and the third surface of the prism is 5° or more and 90° or less. It is characterized by certain things.

In a second aspect of the present invention, in the first aspect, a diffusion surface of the diffusion plate is provided on a side facing the prism, and a surface of the diffusion plate opposite to the diffusion surface is formed in a planar shape. It is characterized by the presence of

A third invention is based on the second invention, wherein the diffusion surface of the diffusion plate is formed in the shape of a groove in which a plurality of concave portions and convex portions are arranged adjacent to each other.

A fourth invention is based on the third invention, wherein the prism is formed in an extruded shape with a constant cross-sectional shape, and the groove portion of the diffusion surface of the diffusion plate extends substantially parallel to the extrusion direction of the prism. It is characterized by the presence of

A fifth invention is based on the third or fourth invention, wherein a light diffusion angle in a direction substantially parallel to the groove direction of the diffusion plate is smaller than a light diffusion angle in a direction substantially perpendicular to the groove direction of the diffusion plate. It is characterized by this.

A sixth invention is characterized in that, in any one of the first to fifth inventions, the two diffusion plates are arranged with a predetermined gap between them.

A seventh invention is characterized in that, in any one of the first to sixth inventions, the light spread angles of the two diffusion plates are each 90° or more.

An eighth invention is the light source, the prism, and a transparent cover disposed outside the two diffusion plates in any one of the first to seventh inventions, and the transparent cover includes a It is characterized by having a substantially parallel surface on which the light emitted from the diffuser plate enters and faces the diffuser plate.

A ninth invention is characterized in that in any one of the first to eighth inventions, the light source is a laser light source.

According to the present invention, light loss at the diffuser plate is small, and light can be uniformly emitted with a wide radiation angle.

FIG. 1 is a schematic diagram showing the configuration of a laser projection device according to the present embodiment. FIG. 3 is a partially enlarged cross-sectional view showing the configuration of a diffuser plate. It is a figure showing the light beam of a laser projection device. FIG. 3 is a diagram showing light diffusion due to refraction at a diffuser plate. FIG. 3 is a diagram showing the radiation angle distribution of light emitted from the slope of a prism. It is a figure which shows the radiation angle distribution of the emitted light of a diffuser plate. It is a figure which shows the radiation angle distribution as a laser projection apparatus when the light flux of a diffuser plate is superimposed.

Embodiments of the present invention will be described below based on the drawings. Note that the following description of preferred embodiments is essentially just an example, and is not intended to limit the present invention, its applications, or its uses.

FIG. 1 is a schematic diagram of a laser projection device according to this embodiment. In FIG. 1, the right-hand direction in the paper is the X-axis, the upward direction is the Y-axis, and the depth direction in the paper is the Z-axis.

As shown in FIG. 1, the laser projection device 100 includes a laser light source 101, a prism 102, a diffusion plate 106 and a diffusion plate 111, and a transparent case 112.

The laser light source 101 emits light in the positive direction of the X-axis. The distribution of the emitted light has a radiation distribution close to a Gaussian distribution with the center of the radiation distribution parallel to the X axis. The spread angle of the laser light source 101 is preferably 5° or more and 40° or less in full width at half maximum. If possible, the angle should be 30° or less.

The wavelength of the laser light source 101 is a near-infrared monochromatic wavelength, and is not detected by the human eye when emitting light. The laser light source 101 has a plurality of laser light emitting elements (not shown) arranged closely in the YZ plane. By arranging a plurality of laser emitting elements, it is possible to weaken spatial coherence and reduce speckle noise.

Furthermore, by using a laser as a light source, the response can be made higher than that of an LED, and pulsed light with a short emission time can be formed. As a result, even if the average energy is the same, by increasing the peak light intensity, it is possible to irradiate and measure distant objects in distance measurement and the like.

The prism 102 has a triangular cross section in the XY plane, and has an extruded shape with a constant cross-sectional shape in the Z-axis direction. In other words, the side including the apex of the triangle of the prism 102 is parallel to the Z-axis direction of any apex corner.

A bottom surface 103 of the prism 102 is arranged to face the laser light source 101 and is parallel to the YZ plane. The apex angle θ formed by the slopes 104 and 105 of the prism 102 is set to be 90° or less and at an angle that totally reflects the light from the laser light source 101. Note that if the apex angle θ is too small, the strength will be insufficient and it will be easy to break, so it is desirable that the apex angle θ is 5° or more.

The prism 102 is transparent at the wavelength of the laser light source 101, and its material may be, for example, resin such as polycarbonate or acrylic, or glass.

With respect to the emission center of the laser light source 101, a line connecting the center position of the bottom surface of the prism 102 and the apex of the prism 102 is slightly shifted.

The diffusion plate 106 is made of a thin flat member. Diffusion plate 106 is arranged to face slope 104 of prism 102 . The groove portion 108 of the diffusion plate 106 is located on the prism 102 side, and the surface opposite to the groove portion 108 is the flat portion 107.

The diffusion plate 111 is a diffusion plate similar to the diffusion plate 106, and is arranged to face the slope 105 of the prism 102, and the groove portion of the diffusion plate 111 is on the prism 102 side.

The diffuser plate 106 and the diffuser plate 111 are transparent at the wavelength of the laser light source 101. The material may be, for example, resin such as polycarbonate or acrylic, or glass.

Diffusion plate 106 and diffusion plate 111 are arranged with a predetermined gap d in between. The distance between the gaps d is at least 0.05 mm. By providing the gap d, it is possible to reduce the risk of dust generation and damage caused by contact between the diffusion plate 106 and the diffusion plate 111.

The light amount center 140 indicates the center of the light amount of the radiation distribution of light exiting the prism 102. The surface normal 141 of the diffuser plate 106 is shifted clockwise around the Z-axis by an angle φ with respect to the light amount center 140. The angle φ is approximately 1/2 of the spread angle of the laser light source 101.

The transparent case 112 has a triangular cross-sectional shape in the XY plane. Opposing surfaces of the transparent case 112 and the diffusion plate 106, and of the transparent case 112 and the diffusion plate 111, are substantially parallel.

FIG. 2 is an enlarged view of a portion surrounded by a virtual circle A shown in FIG. As shown in FIG. 2, the groove 108 of the diffusion plate 106 has a shape in which a recess 109 and a projection 110 are arranged adjacent to each other, and the combination of the recess 109 and the projection 110 is repeated at a period p.

The groove portion 108 has an extruded shape with a constant cross-sectional shape in the Z-axis direction. In other words, the sides including the triangular vertices are parallel to the groove direction of the groove 108 at any apex corner.

The concave portion 109 and the convex portion 110 have an aspherical shape, the inclination angle of the portion where the concave portion 109 and the convex portion 110 contact is the same, and the concave portion 109 and the convex portion 110 are smoothly joined. The shape of the concave portion 109 rotated 180 degrees around the Z-axis is similar to the convex portion 110 . In the XY plane, a line 145 passing through the connection between the concave portion 109 and the convex portion 110 is perpendicular to the normal direction of the groove portion 108 . Note that the groove shape of the diffusion plate 111 is similar to that of the diffusion plate 106.

The operation of the laser projection device 100 will be described below. As shown in FIG. 3, the emitted light 120 from the laser light source 101 enters the prism 102 through the bottom surface 103 and is refracted to become a light beam 121. Since the apex angle θ of the prism 102 is smaller than 90° and is set to be totally reflected on the slope 105, most of the light ray 121 is totally reflected on the slope 105 and is reflected on the slope 104 opposite to the slope 105. incident.

Since the light ray 121 is incident at an angle close to the normal direction of the slope 104, most of the light passes through the slope 104 and exits from the prism 102. The light beam 121 emitted from the slope 104 of the prism 102 enters the groove 108 of the diffuser plate 106.

FIG. 4 is an enlarged view of the portion surrounded by the virtual circle B shown in FIG. As shown in FIG. 4, the groove portion 108 includes a concave portion 109 and a convex portion 110. The light ray 122 incident on the concave portion 109 is diffused due to the concave lens effect. The light beam 123 incident on the convex portion 110 is once condensed, but then diffused.

The light diffused by the groove portion 108 of the diffuser plate 106 is refracted by the flat portion 107 of the diffuser plate 106 and exits. Since the refractive index of the diffuser plate 106 is higher than that of air, the light emitted from the diffuser plate 106 has a wider spread angle. Therefore, the light ray 121 incident on the groove 108 in which the concave portion 109 and the convex portion 110 are arranged is diffused by the refraction effect. The same applies to light that is totally reflected on the slope 104 of the prism 102, transmitted through the slope 105, and diffused by the diffusion plate 111.

5A to 5C are diagrams showing the radiation angle distribution of the emitted light from the laser projection device 100 on the XY plane in FIG. 1. In FIG. 1, the direction of rotation from the Y-axis to the X-axis around the Z-axis is positive.

FIG. 5A is a diagram showing the radiation angle distribution of light emitted from the slopes 104 and 105 of the prism 102. As shown in FIG. 5A, the light emitted from the laser light source 101 is split by the prism 102 into two light beams 130 and 131 corresponding to the light emitted from the slopes 104 and 105.

FIG. 5B is a diagram showing the radiation angle distribution of the emitted light from the diffuser plate 106 and the diffuser plate 111. The light emitted from the slopes 104 and 105 of the prism 102 becomes a light beam 132 and a light beam 133 by being diffused by the diffusion plate 106 and the diffusion plate 111.

Although the light beam 132, which is the light diffused from the diffuser plate 106, has a spread in the negative direction of the radiation angle distribution, the spread angle of the diffuser plate 106 is set so that it slightly straddles the positive direction. Similarly, the beam 133, which is the light diffused from the diffuser plate 111, has a spread in the positive direction of the radiation angle distribution, but the spread angle of the diffuser plate 111 is set so that it slightly straddles the negative direction.

The radiation angle distribution of the luminous flux 134 of the emitted light from the diffuser plate 106 is such that the light intensity is high in the negative direction, and the light intensity in the 0° direction is low (see FIG. 5C). This occurs because, in FIG. 2, the center 140 of the amount of light emitted from the prism 102 is incident on the surface normal 141 of the groove 108 of the diffuser plate 106 at an angle φ within the XY plane.

Since the light amount center 140 of the emitted light from the prism 102 is incident on the groove 108 at an angle φ, the angle of incidence becomes smaller with respect to the slope 146 of the groove 108, and the change in the angle of the light beam due to refraction is reduced. . That is, the diffusion at the diffusion plate 106 becomes smaller. Since the refracted light at the slope 146 of the groove portion 108 is light that diffuses in the negative direction of the radiation angle distribution, the angular spread in the negative direction becomes small (see reference numeral 150 in FIG. 5B).

On the other hand, as the incident angle increases with respect to the slope 147, the change in the angle of the light beam due to refraction increases. That is, the diffusion at the diffusion plate 106 increases. Since the refracted light at the slope 147 of the groove portion 108 is light that is diffused in the positive direction of the radiation angle distribution, the angle spread in the positive direction becomes large (see reference numeral 151 in FIG. 5B).

When the light amount center 140 is inclined at an angle φ with respect to the surface normal 141, the amount of light to the slope 146 is larger than that to the slope 147, and the light diffusion is smaller. Therefore, in the radiation angle distribution, the light intensity in the negative direction becomes larger. Therefore, the radiation angle distribution of the light emitted from the diffuser plate 106 has a strong light intensity in the negative direction. Note that, in the light emitted from the diffuser plate 111, the light intensity on the forward direction side is similarly increased.

FIG. 5C shows the radiation angle distribution of the laser projection apparatus 100 when the light beam 132 of the diffuser plate 106 and the light beam 133 of the diffuser plate 111 are superimposed. The light beam 132 diffused from the diffuser plate 106 is set so as to spread not only in the negative direction but also partially in the positive direction (see FIG. 5B). Similarly, the diffused light beam 133 from the diffuser plate 111 is set to spread not only in the positive angular direction but also partially in the negative angular direction (see FIG. 5B).

Therefore, as shown in FIG. 5C, by superimposing the light beams 132 and 133, we can create a radiation distribution where the light intensity near 0° is a little low and the light intensity is high in the positive and negative directions, as in the case of the light beam 134. Obtainable.

Such a radiation distribution is advantageous when observing the positive direction and the negative direction, that is, the peripheral area, from the 0° direction, that is, the front direction of the laser projection device 100. By setting the spread angles due to diffusion of the diffuser plate 106 and the diffuser plate 111 to 90° or more, the combined spread angle can be 180° or more.

On the other hand, the radiation distribution in the XZ plane remains the same as the spread angle of the laser light source 101. When installing the laser projection device 100 in a car or the like, by setting the XZ plane in the vertical direction and the XY plane in the horizontal direction, the light does not spread much in the vertical direction but spreads in the horizontal plane, increasing the efficiency of light. It can be irradiated well.

By the way, when calculating the laser class of the laser light source 101, the beam diameter at the diffuser plate of the projection optical system is involved in the laser class calculation. In this embodiment, since the prism 102 splits the light into two and diffuses each, it appears that the laser light source 101 is divided into two, and in the laser class calculation, the laser becomes laser class 1. The upper limit of light source output can be improved.

The diffusion plate 106 and the diffusion plate 111 can be manufactured by injection molding using a mold. In this embodiment, the grooves 108 of the diffuser plate 106 and the diffuser plate 111 have smooth curves and extruded shapes, so that the mold can be easily manufactured by machining in a short time using a shaper, for example. Diffusing plates can be manufactured at low cost by injection molding. Further, the diffusion plates 106 and 111 are less susceptible to deformation due to abrasion during the manufacturing process and poor transfer of molding.

Furthermore, since the grooves 108 of the diffuser plate 106 and the diffuser plate 111 are formed with smooth curves, the angle of inclination becomes locally large at the edges, for example, resulting in unnecessary reflection or stray light near the edges. Never. Further, the light efficiency of the diffuser plate does not tend to decrease due to unexpected spread of diffusion due to wear of the edge portions.

The diffuser plate 106 and the diffuser plate 111 are arranged with a gap d between them, but since the light from the laser light source 101 is divided into two by the prism 102 and becomes light with an angle, the light from the prism 102 is Almost no emitted light is directed in the 0° direction (see FIG. 5A). Therefore, almost no light leaks from the gap d between the diffuser plate 106 and the diffuser plate 111.

By the way, in general, if an error occurs during assembly, it is difficult to align the center of the radiation distribution of the laser light source 101 with the axis of symmetry of the prism 102.

On the other hand, in the present embodiment, the radiation distribution of the laser light source 101 is a Gaussian distribution and has a spread of at least 5° or more in full width at half maximum, and the radiation distributions of the diffuser plate 106 and the diffuser plate 111 overlap at an angle of 0°. .

Therefore, even if the center of the radiation distribution of the laser light source 101 and the axis of symmetry of the prism 102 deviate, the light intensity in the 0° direction is unlikely to become 0. Here, as the spread angle of the radiation distribution of the laser light source 101 is increased, the tolerance for the deviation between the center of the radiation distribution of the laser light source 101 and the axis of symmetry of the prism 102 can be increased.

According to such a configuration, the emitted light from the laser light source 101 is divided into two by the prism 102, diffused by the diffusing plate 106 and the diffusing plate 111 that use two refractions, and the diffused light is overlapped, so that the diffusing plate 106 and the diffuser plate 111 are small, and light with a spread angle of 180° or more can be emitted.

Furthermore, by dividing the light source image of the laser light source 101 into two, the apparent light source emission size can be increased and the laser output for laser class 1 can be increased, thereby providing a laser projection device capable of bright illumination. can do.

《Other embodiments》
The embodiment described above may have the following configuration.

In this embodiment, the laser light source 101 is one in which a plurality of laser light emitting elements are arranged to reduce spatial coherence, but a laser light source 101 with low spatial coherence, such as a multi-mode semiconductor laser, is used. It's okay. Alternatively, a light emitting diode or a light emitting diode (SLD) with a small emission diameter may be used.

Note that a single mode type semiconductor laser may be used if an increase in speckle noise is not a problem. Furthermore, if the device does not need to be large-sized, HeNe, argon gas laser, or the like may be used.

Further, in this embodiment, the wavelength of the laser light source 101 is near infrared, but visible light may be used if it is acceptable for the measurement light to be visible. Alternatively, ultraviolet light may be used. Note that although the laser light source 101 is used as the light source, an LED may also be used, although the response characteristics will be poor.

Further, in this embodiment, an antireflection film may be formed on the flat portions 107 of the diffusion plate 106 and the diffusion plate 111 to reduce surface reflection.

Further, in this embodiment, the diffuser plate 106 and the diffuser plate 111 may have the same spread angle, or may have different spread angles by changing the shape of the recess 109 and the protrusion 110 of the groove 108.

Further, in this embodiment, the cross-sectional shape of the prism 102 may be an isosceles triangle or a scalene triangle.

Further, in the present embodiment, the transparent case 112 has a triangular cross section, but is not limited to this shape. For example, although the radiation angle distribution changes slightly due to a lens effect, it may have a cylindrical shape that is a semicircle in the XY plane of FIG. 1.

Further, in this embodiment, in order to spread the light in the XZ plane direction, a diffusion plate that diffuses the light in the XZ plane may be placed immediately after the laser light source 101.

The projection device of the present invention has low light loss at the diffuser plate, can emit light with a wide radiation angle, and divides the apparent beam at the exit surface of the projection device to increase the laser light source output within the laser class 1 range. Therefore, it can be applied to outdoor vehicle sensors and security sensors, and indoor light sources for distance sensors in home appliances such as air conditioners and lighting.

100 Laser projection device 101 Laser light source 102 Prism 103 Bottom surface (first surface)
104 Slope (second surface)
105 Slope (3rd surface)
106 Diffusion plate 108 Groove portion 109 Recessed portion 110 Convex portion 111 Diffusion plate 112 Transparent case

Claims (9)

a light source that emits light in a predetermined X-axis direction;
a prism having a triangular cross section in the XY plane, where the two directions perpendicular to the X-axis direction are the Y-axis direction and the Z-axis direction, respectively;
A surface parallel to the YZ plane of the prism and on which light from the light source enters is a first surface, and two slopes different from the first surface are second and third surfaces, respectively.
comprising two diffusion plates disposed opposite to each other on the second surface and the third surface of the prism,
The apex angle formed by the second surface and the third surface of the prism is 5° or more and 90° or less,
The light totally reflected by the second surface is made to enter the third surface, and the light totally reflected by the third surface is made to be made to enter the second surface, so that the light from the light source is split into two. west,
Light is incident on the two diffusion plates facing the second surface and the third surface, and is diffused and transmitted, and the two diffused lights are superimposed.
A projection device characterized by: In claim 1,
A diffusion surface of the diffusion plate is provided on a side facing the prism,
A projection device characterized in that a surface of the diffusion plate opposite to the diffusion surface is formed into a planar shape. In claim 2,
A projection device characterized in that the diffusion surface of the diffusion plate is formed in the shape of a groove in which a plurality of concave portions and convex portions are arranged adjacent to each other. In claim 3,
The prism is formed into an extruded shape with a constant cross-sectional shape,
A projection device characterized in that the groove portion of the diffusion surface of the diffusion plate extends substantially parallel to the extrusion direction of the prism. In claim 3 or 4,
A projection device characterized in that a light diffusion angle in a direction substantially parallel to the groove direction of the diffusion plate is smaller than a light diffusion angle in a direction substantially perpendicular to the groove direction of the diffusion plate. In any one of claims 1 to 5,
The projection device is characterized in that the two diffusion plates are arranged with a predetermined gap between them. In any one of claims 1 to 6,
A projection device characterized in that each of the two diffusion plates has a spread angle of 90° or more. In any one of claims 1 to 7,
a transparent cover disposed outside the light source, the prism, and the two diffusion plates;
The projection device is characterized in that the transparent cover has a substantially parallel surface on which the light emitted from the diffuser plate enters and faces the diffuser plate. In any one of claims 1 to 8,
A projection device characterized in that the light source is a laser light source.

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